Add VariantMap parse instantiations

Author: Belzedar94

src/variant.cpp

@@ -296,4 +296,11 @@ std::vector<std::string> VariantMap::get_keys() {
   return keys;
 }
 
+// Explicit instantiations keep linkers happy in builds that still reference
+// VariantPath parsing entry points.
+template void VariantMap::parse_istream<true>(std::istream&);
+template void VariantMap::parse_istream<false>(std::istream&);
+template void VariantMap::parse<true>(const std::string&);
+template void VariantMap::parse<false>(const std::string&);
+
 } // namespace Stockfish